This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Human immunodeficiency virus type 2 (HIV-2) emerged following cross-species transmission of SIV from sooty mangabeys to humans several decades ago in West Africa. The epidemic groups of HIV-2 are HIV-2 Group A and Group B. These 2 groups have been established in the human population for at least 50 years. However, it is likely that new divergent strains of SIV can infect humans and lead to new outbreaks. We isolated characterized a new HIV-2 group F, HIV2-NWK08F, in 2008 from an immunodeficient person from Sierra Leone who immigrated to the USA in 2007. Health care providers in Sierra Leone and elsewhere need to be alerted that a strain of HIV-2, which is not detected by PCR for epidemic HIV-2 strains, exists and can lead to immunosuppression. This is the first HIV-2 to emerge from an Anglophone African country.